function isValidEmail(str) {
return (str.indexOf(".") >= 0) && (str.indexOf("@") >= 0);
}

function CheckDataesub()
{
with(document.frmemailsub)
{
if(email.value == "")
{
alert("Please Provide Your EMail Address");
email.focus();
email.value="";
return false;
}
if (!isValidEmail(subscribe.value)) 
{
alert("Please Provide Valid EMail Address");
email.focus();
email.value="";
return false;
}
}
return true;
}